The present invention relates to a torque-dividing transmission, particularly for aircraft.
As is known, a torque-dividing transmission is interposed between the engine assembly and propulsive member of an aircraft, and normally comprises a single input pinion fitted to the output shaft of the engine assembly, a single output gear fitted to the shaft of the propulsive member, and two or more gear assemblies or branches for transmitting the input torque between the pinion and the output gear. The gear assemblies are arranged parallel to one another so as each to transfer, in use, to the shaft of the propulsive member a respective portion of the torque transmitted by the input shaft, and define, together with the pinion and the output gear, two or more respective speed reduction stages.
In known transmissions of the above type, on account of errors in both the form and position of the various parts of the transmission, the torque from the input pinion normally follows preferential routes, as opposed to being divided equally between the various branches of the transmission, so that it is impossible to determine the actual stress of each of the various gear assemblies or branches.
To overcome the above drawback, a torsion shaft is interposed between the reduction stages of each branch to compensate, by twisting, the above errors so that the input torque is divided acceptably between the various branches of the transmission.
Using torsion shafts, however, results in a considerable increase in length on account of the normally long length of the torsion shafts themselves. Moreover, as the gears of the torsion shafts must necessarily be supported independently, each branch, i.e. each torsion shaft, must be provided with at least four bearings, which inevitably increases the weight and size and impairs the reliability of the transmission.
Alternatively, the aforementioned drawbacks are eliminated using a floating self-centering input pinion for dividing the torque between the various branches. A floating pinion, however, allows for a maximum of three, as opposed to any number of, gear assemblies or branches, and numerous problems are encountered in controlling the position of the pinion, particularly in the event of a malfunction in one of the branches.